Key Engineering Materials Vol. 992

Abstract: The development of energy storage capacitors with high dielectric constant and good stability has been focused on by researchers due to many issues regarding environmental protection and energy conservation. Barium-Strontium Titanate based ceramic capacitors are widely used for energy storage applications due to their attractive dielectric properties. In this study, (Ba_0.90Sr_0.10) TiO₃ based capacitors were produced, and the influence of additives i.e. CaZrO₃, MnCO₃, CeO₂, ZnO, and Nb₂O₅ was investigated. The parameters of all the fabrication processes have been optimized to get defect-free green and sintered samples. The defect-free green parts were sintered at 1380°C for 2 h and perovskite structure was confirmed by XRD profiles. The grain size was refined from 25 μm to 08 μm analyzed by scanning electron microscopy (SEM). The capacitor was tested at 40 KV successfully and capacitance of 2.0 nF was measured at this high voltage. The results showed that high-voltage capacitors can be fabricated with enhanced energy storage.

Abstract: Now a days, demand for electrical energy is increasing because most of our gadgets and devices based on electricity. Due to the depletion of fossil fuel much more attention is given to renewable energy sources and devices to store that energy. Between these energy storage devices electrochemical energy storage devices has got more attention and among electrochemical energy storage devices, batteries are dominant, but they experience some safety issue, slow charge transfer and cannot meet high power requirement for numerous applications. Thus, as compare to batteries supercapacitor have high power density and fast charge transfer. So much more attention is going on to increase the performance of supercapacitors. In this study, hydrothermal method is used to synthesis rGO/NiO composite and electrospinning to fabricate rGO/NiO composite nanofibers. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) is performed to study morphological and structural properties. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are performed to study the electrochemical behavior. Reduced graphene oxide shows specific capacitance as low as 91.6 F/g. NiO nanostructures, rGO/NiO composite and rGO/NiO composite nanofibers shows specific capacitance of 256.4 F/g, 537.8 F/g and 663.8 F/g respectively.

Abstract: The production of hydrogen through electrochemical water splitting using renewable energy sources shows promise in achieving net-zero emissions. This process requires a catalyst for the electrochemical splitting of water into hydrogen and oxygen. Many studies are dedicated to discovering efficient catalysts for water-splitting reactions that do not depend on noble metals. Integrating metal nanoparticles into laser-induced graphene has proven to deliver high catalytic performance, attributed to the high surface area and efficient charge transfer enabled by the highly conductive nature of laser-induced graphene. However, optimization of the laser-induced graphene electrodes is necessary for their effective use in water-splitting reactions. This study optimized the 405nm visible laser parameters to tune the Reduced polyimide-derived RPI laser-induced graphene electrodes for driving a water-splitting reaction. The optimization of the laser parameters revealed that a laser power of 5W, 10W, and 15W, engraving speeds of 1000 mm/min, 2000 mm/min, 3000 mm/min, and 4000 mm/min, and line-to-line tracing 20 line/mm, 18 line/mm and 15 line/mm with horizontally and vertically settings provides the optimum electrodes for water-splitting reaction.

Abstract: As global climate change intensifies, a pivotal shift towards renewable energy sources becomes imperative. Given its adaptability and efficacy, solar cell technology stands out as a frontrunner in the quest to combat environmental degradation. With the vast expanse of buildings occupying significant portions of the urban landscape, integrating photovoltaics into building design is a timely necessity. Before embarking on tangible installations, conducting an energy simulation proves invaluable in gauging a building's energy requirements, ensuring cost and time efficiency. This paper delves into the advanced materials employed in solar cell technology and undertakes an energy simulation for a photovoltaic module. Building-Integrated Photovoltaics is not just an innovative leap in harnessing solar energy but also symbolizes the synergy between architectural design and energy production. By fine-tuning system operations and comprehending external factors, Building-Integrated Photovoltaics points to a future where energy solutions are both sustainable and tailored to a wide range of applications.

Abstract: To meet the requirements of second generation photovoltaics, spin coating and RF magnetron sputtering techniques have been utilized to fabricate zinc sulfide thin films for buffer layer optimization. During fabrication process, substrate temperatures for spin coating and RF magnetron sputtering processes are kept at room temperature and at 200 oC, respectively. Thin films are annealed at 500oC for 1 hour in an inert environment to acquire crystallinity and uniform surface morphology. XRD analysis reveals that thin films fabricated by spin coating and RF magnetron sputtering exhibit wurtzite and zinc blende crystal structures, respectively. SEM shows that the surface morphology of thin films fabricated by both techniques is uniform and homogeneous without voids and cracks. EDS results indicate that thin films fabricated via spin coating have equal stoichiometric ratio of zinc to sulfur (1:1). Whereas, an unequal stoichiometric ratio of zinc to sulfur is detected in RF magnetron sputtered thin films. According to optical studies, spin coated zinc sulfide thin films have 67% transmission with an energy band gap of 3.62 eV. While, RF magnetron sputtered thin films have 76% transmission with a wide energy band gap of 3.70 eV. Electrical properties depict that thin films fabricated by RF magnetron sputtering have higher carrier concentration, lower resistivity and higher conductivity than spin coated thin films. In comparison, RF magnetron sputtered zinc sulfide thin films exhibit best structural and optoelectronic properties for buffer layer in second generation solar cells.

Abstract: Thermal and photo instabilities are two major issues for organic-inorganic lead halide perovskite solar cells. Mixing of A site cations and X cite halogens are tried to address these issues, but the performance is still not reached the theoretical Shockley Quissier limit. One of the reasons for this is the energy loss ratio with band gap energy. Despite the high open circuit voltage, this ratio is lower for perovskite solar cell in competition with silicon technology. Open circuit voltage can be increased by different ways, but short circuit current is compromised. To increase open circuit voltage without affecting the short circuit current is the surface passivation technique. Numerous studies have been conducted on electron transport layer and perovskite interface, with a very few on hole transport layer and perovskite interface. Both interfaces are equally important. Here we passivated the later interface by inserting a 10 nm thick layer of caesium-formamide based lead mixed halide perovskite in FAMA mixed perovskite solar cell. Our proposed model achieved an efficiency of 31.42 % with a high fill factor of 86.4 %. At the same time, we recorded higher open circuit voltage of 1.46 V and 25.49 mA/cm² short circuit current. Our proposed model will help in experimental work for making highly efficient perovskite solar cells.

Abstract: This study investigated the impact from nitrogen content in backing gases on the microstructure and corrosion resistance of food grade stainless steel weld metal. Three types of backing gases were employed: 100%Ar, 85%Ar+15%N₂, and 100%N₂. Statistical analysis using ANOVA revealed a significant effect from nitrogen content on the ferrite phase fraction within the weld metal microstructures (p-value = 3.5E-05), indicating a reduction in the ferrite phase with increasing nitrogen content. Moreover, increasing nitrogen content positively shifted the pitting corrosion potential, indicating enhanced corrosion resistance. Optical microscopy confirmed lower pit density in samples with nitrogen backing gas as compared with samples with argon backing gas. These findings underscore the crucial role of nitrogen content in backing gases at influencing microstructure and corrosion resistance in stainless steel weld metal, with higher nitrogen levels correlated with improved corrosion resistance.

Abstract: The present study is an attempt to provide the solutions to the problem encountered by the components subjected to metal-to-metal wear or galling from grass root level to the advanced stages. Sliding wear or metal to metal wear, galling, can result in seizure due to bonding of the materials and can generate large amounts of damage over small sliding distances. More damage could be expected under unlubricated sliding systems. At lower loads, and particularly at high relative velocities could lead to considerable heating of the metallic surfaces, oxide growth and stripping can also be possibly observed. Under similar conditions cobalt based and nickel based hard facings were considered to be most suited, but due to the high cost of these materials an attempt has been made to achieve adequate hardness and wear resistance at much lower cost, by alloy additions with the help of Shielded Metal Arc Welding (SMAW) process. In this paper the effect of alloying elements on the wear performance of hard-faced components prepared by Shielded Metal Arc Welding (SMAW) process has been undertaken on the low carbon steel substrate by different compositions of iron (Fe) based, hard facing electrodes. The effect of alloying elements especially with varying compositions of chromium and molybdenum on the microstructure, microhardness, and wear resistance of the Fe-based hardfacing alloyed specimens were investigated by means of optical microscopy, and pin on disc wear test. The hardness and wear resistance were improved with the addition of principal alloying elements such as chromium (Cr), molybdenum (Mo) and manganese (Mn) through the consumable electrode during hardfacing by SMAW process. The microhardness of substrate material, i.e., before hardfacing was around 100 HV that latter improved up to 280 HV using first electrode E1, 330 HV using second electrode E2 and 350 HV using third electrode E3. Sliding wear for metal-to-metal wear testing was conducted as per ASTM G99 standards and wear resistance was calculated in terms of the weight loss of the pin after the test run. Wear resistance was found to be improved by 45% approximately with the electrodes E1 and E2 which have chromium content from 2.5% to 4.5 %, whereas an improvement up to 54% was observed with the third electrode E3 corresponding to 6% chromium. The percentage of carbide was found to be more in hardfaced layer in the presence of the molybdenum (Mo). The improvement of hardness and wear resistance of the hardfacing layer is attributed to the solution strengthening of Mo alloying elements. It was further observed that samples that have higher Cr content possessed finer grains with martensitic structure. Role of Mn can also be very important as it removes oxygen and Sulphur from the coatings and improve toughness and overall strength, on the other hand presence of silicon (Si) can attribute to improved yield strength.

Abstract: Copper is used in various industrial fields due to its characteristics and properties. The very high thermal conductivity of copper makes it difficult to weld it using conventional fusion welding processes. Friction stir welding FSW is a solid-state joining process of metallic materials, which can be used to perform copper welded joints. Using a liquid working environment in FSW welding (submerged friction stir welding SFSW) causes the decrease of the process temperature, which can be beneficial for copper. The paper presents aspects and results obtained by ISIM Timisoara regarding FSW and SFSW butt welding of copper Cu99 2.5 mm thick, using the same type of the welding tool. The obtained results will be useful for the start of the experimental researches of processing in air and in liquid environment FSP and SFSP of copper Cu99, which will be performed in the Nucleu PN 23 37 01 02 project underway at ISIM Timisoara.